Rust is everything and you are in Michigan. Check thoroughly underneath. If the frame rails or spring perches are rusted thru, it is almost worthless.
In 1966, the K-frame is the same for slant and V-8, but I understand the V-8 steering center-link drops a bit lower to clear the pan. I have a slant and V-8 and that part looks pretty similar. You will need the motor mounts that came with the engine, and I think the later mounts (1973+?) are different with a spool.
You will need to fold in a sheet-metal lip in the trans tunnel for a 727 to clear. An easy hammer job. You will need to shorten the 727's driveshaft since early-A's are shorter wheelbase. Driveline shops can easily do that.
You will need a rare SBP 8-3/4 rear, carry 2 spare tires, or change your front end to 73+ BBP, which many do anyway to get cheap disk brakes.
As many say, a simple job, just keep the shell and change the entire power-train and suspension. I am staying with a slant in my 64 Valiant. Gas is $4.25/gal today in CA.